- Acylation of anisole with carboxylic acids catalyzed by tungsten oxide supported on titanium dioxide
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Friedel-Crafts (F-C) acylation of anisole with octanoic acid was carried out on tungsten oxide (WO3) supported on various types of oxide supports. We have found that the highest activity was obtained when TiO2 was used as the support. WO3/TiO2 was found to be active in the acylation of anisole with carboxylic acids of varying alkyl chain lengths (C6–C10). It was possible to recycle the WO3/TiO2 catalyst for up to 5 times without deactivation. The turnover frequency (TOF) of the catalyst was closely correlated with the electronegativity of the cation of the support used for WO3. When a strong basic oxide such as CeO2 was used as a support, the acid strength of WO3 was diminished, while the strong acidity of WO3 was retained on a weak basic support like TiO2. This explains why the acid strength and consequently, the activity, were found to be the highest for the WO3/TiO2 catalyst. The trend of the catalytic performance was consistent with the order of acid strength of WO3 on different supports measured by temperature-programmed desorption of NH3.
- Okumura, Kazu,Iida, Masaki,Yamashita, Hajime
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- Isolation and Characterization of Regioisomers of Pyrazole-Based Palladacycles and Their Use in α-Alkylation of Ketones Using Alcohols
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Regioisomers of 3,5-diphenyl-1-(4-(trifluoromethyl)phenyl)-1H-pyrazole-based palladacycles (1 and 2) were synthesized by the aromatic C-H bond activation of N/3-aryl ring. The application of these regioisomers as catalysts to enable the formation of α-alkylated ketones or quinolines with alcohols using a hydrogen borrowing process is evaluated. Experimental results reveal that palladacycle 2 is superior over palladacycle 1 to catalyze the reaction under similar reaction conditions. The reaction mechanisms for the palladacycles 1 and 2 catalyzed α-alkylation of acetophenone were studied using density functional theoretical (DFT) methods. The DFT studies indicate that palladacycle 2 has an energy barrier lower than that of palladacycle 1 for the alkylation reaction, consistent with the better catalytic activity of palladacycle 2 seen in the experiments. The palladacycle-phosphine system was found to tolerate a wide range of functional groups and serves as an efficient protocol for the synthesis of α-alkylated products under solvent-free conditions. In addition, the synthetic protocol was successfully applied to prepare donepezil, a drug for Alzheimer's disease, from simple starting materials.
- Mamidala, Ramesh,Samser, Shaikh,Sharma, Nishant,Lourderaj, Upakarasamy,Venkatasubbaiah, Krishnan
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supporting information
p. 3343 - 3351
(2017/09/18)
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- Catalytic Ring-Opening of Cyclic Alcohols Enabled by PCET Activation of Strong O-H Bonds
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We report a new photocatalytic protocol for the redox-neutral isomerization of cyclic alcohols to linear ketones via C-C bond scission. Mechanistic studies demonstrate that key alkoxy radical intermediates in this reaction are generated via the direct homolytic activation of alcohol O-H bonds in an unusual intramolecular PCET process, wherein the electron travels to a proximal radical cation in concert with proton transfer to a weak Br?nsted base. Effective bond strength considerations are shown to accurately forecast the feasibility of alkoxy radical generation with a given oxidant/base pair.
- Yayla, Hatice G.,Wang, Huaiju,Tarantino, Kyle T.,Orbe, Hudson S.,Knowles, Robert R.
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supporting information
p. 10794 - 10797
(2016/09/09)
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- Solvent-free catalytic Friedel - Crafts acylation of aromatic compounds with carboxylic acids by using a novel heterogeneous catalyst system: p-Toluenesulfonic acid/graphite
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TsOH/graphite was found to be an effective catalyst system for the Friedel-Crafts acylation of aromatic compounds with carboxylic acids. Both aliphatic and aromatic carboxylic acids reacted smoothly under TsOH/graphite catalysis to afford the corresponding aromatic ketones in high yields. The graphite was easily recovered by simple extraction and could be reused without decrease of activity in the presence of fresh TsOH.
- Sarvari, Mona Hosseini,Sharghi, Hashem
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p. 2282 - 2287
(2007/10/03)
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- Simple and improved procedure for the regioselective acylation of aromatic ethers with carboxylic acids on the surface of graphite in the presence of methanesulfonic acid
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Friedel-Crafts acylation of aromatic compounds such as anisole has been successfully carried out using the combination of graphite with MeSO 3H. Both aromatic and aliphatic carboxylic acids reacted smoothly under the conditions to afford the corresponding aromatic ketones in high yield.
- Sarvari, Mona Hosseini,Sharghi, Hashem
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p. 2165 - 2168
(2007/10/03)
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